Chemotherapy: Open Access
Open Access

Abstract

Targeting the PD-1 Pathway in MSI-Stable Metastatic Colorectal Cancer

Kaijun Huang and Jennifer Wu

In patients with microsatellite instability-high (MSI-H) metastatic colorectal cancer (CRC), the inhibition of programmed death-1 (PD-1) pathway has achieved promising response [1]. PD-1 is an immune inhibitory receptor, expressed in many cells, including T cells. Its ligand, PD-L1, is expressed on surface of several cell types, especially tumor cells. When PD-L1 binds to PD-1, an inhibitory signal is transmitted into the T cell, which suppresses T-cell proliferation. MSIH metastatic CRC gives rise to high percentage of mutations which is proportional to mutational load. High mutational load of MSI-H CRC correlates with increased PD-L1 expression which indicates a higher likelihood of response to PD-1 inhibitors, compared to microsatellite instability-stable (MSI-S) CRC [2-4]. Нus, MSI-H CRC could respond to single agent PD-1 pathway inhibition.